Re: -fprofile-update=atomic vs. 32-bit architectures

[Sebastian Huber <sebastian.huber@embedded-brains.de>]

On 08/11/2022 11:25, Richard Biener wrote:
>> It would be great to have a code example for the construction of the "if
>> (f()) f();".
> I think for the function above we need to emit __atomic_fetch_add_8,
> not the emulated form because we cannot insert the required control
> flow (if (f()) f()) on an edge.  The __atomic_fetch_add_8 should then be
> lowered after the instrumentation took place.

Would it help to change the

     if (__atomic_add_fetch_4 ((unsigned int *) &val, 1, __ATOMIC_RELAXED)
== 0)
       __atomic_fetch_add_4 (((unsigned int *) &val) + 1, 1,
__ATOMIC_RELAXED);

into

     unsigned int v = __atomic_add_fetch_4 ((unsigned int *) &val, 1, 
__ATOMIC_RELAXED)
== 0)
     v = (unsigned int)(v == 0);
     __atomic_fetch_add_4 (((unsigned int *) &val) + 1, 1,
__ATOMIC_RELAXED);

to get rid of an inserted control flow?

On riscv this is optimized to:

         li      a4,1
         amoadd.w a5,a4,0(a0)
         addi    a5,a5,1
         seqz    a5,a5
         addi    a4,a0,4
         amoadd.w zero,a5,0(a4)


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